Christopher Biggins, thousands of poshos, John Cooper Clarke, the naughty gents of nature from Caught By The River, Stealing Sheep, Toy and Weatherall... ah, it can only be the Port Eliot Festival

A golf buggy trundles down a track, glinting in the sunlight and kicking up a thin cloud of dust in its wake. Its driver - a portly, grey-haired man in smart dress - speaks firmly, his voice amplified by a megaphone aimed in the direction of a small group of bemused adults and children: "TURN AROUND! YOU ARE GOING THE WRONG WAY! FOLLOW ME TO THE RUBBISH OLYMPICS! COME AND TOSS A PENCIL! HA-HA-HA-HA!" As the buggy bounces past a closer look reveals a grinning, pink face that resembles – actually no, is – that of Sir Christopher Biggins.

Port Eliot is a bit like the huge wedding reception of the richest, most interesting (in a good way) couple you could know: they invite you to their stunningly bucolic Cornish estate and let you swim or canoe in their river, while laying on three and a half days of the most cerebral, eccentric and eclectic entertainment you could hope for. It hardly matters that you aren't sure about some of the other guests. Forget about the family with the croquet set or the man with the iPad tucked into his chinos – John Cooper Clarke is on, and he's talking about getting condoms into Limerick ("They used to be difficult to obtain - they'd smuggle them in in bags of heroin").

The festival mostly eschews big-name acts in favour of a strong focus on the innovative and the influential. Instead of Bruce Springsteen, there is Simon Munnery explaining his distrust of The Boss' lyrics ("when he's not loading crates at the docks, he's being laid off at the factory"), before turning away from the audience and performing a chaotic but brilliant twenty minute, cut-and-stick farce that is filmed shakily by Munnery himself and displayed on screens stage-side, ending with a touching tribute to the crew of the Hindenburg.

Elsewhere, Pete Brown explains his fascination with London's oldest pub ("if you can't get romantic about old coaching inns, you're missing the point"), John Wright leads a foraging walk and Dominic West gleefully quizzes Sanskrit scholar and Yogi, Jim Mallinson ("Have you done it?", grins West, in response to Mallinson explaining that his Yoga guru can imbibe limpets through "both of his orifices").

In the Wardrobe Department, seminal fashion designer Barbara Hulanicki oversees assistants tailoring outfits from multicoloured toilet paper and bin bags. Later on, Rough Trade boss Geoff Travis DJs between bands at the Caught by the River stage which, along with that of fellow curators Five Dials, is hosting some of this summer's most thoughtful and entertaining festival performances.

Roy Wilkinson takes CBTR on Saturday afternoon for one of the weekend's more memorable book readings - featuring a Young Musician of the Year-led Marimba duo who embellish his words with the work of Neil Young and Steve Reich. Attention is then drawn to Five Dials, where Cornish folk band Dalla perform dramatic and celebratory odes to mighty Atlantic waves and blind, itinerant fiddlers. As the sun drops behind the stage, dancers join hands, weaving through the crowd. "The smell of Cornwall is fish, salt and bladderwrack", Dalla tell us, their set a reminder of the hardships Cornwall has endured and the rich, proud culture that heritage has engendered.

That evening, Stealing Sheep blend The Unthanks' beguiling folk with flashes of surfy reverb and whirring synths. It feels like a lot of people are discovering them for the first time, and are very happy about it. Later on The Egg throw out chunks of all-embracing house that has at least one onlooker proclaiming, "Fuck The Bees, I want to watch The Egg!" and abandoning plans to slip away for the second half of the Isle of Wight band's (apparently very good) set on Caught By the River. After that it makes sense to head to the woods and The Boogie Round, where entry is earned through dance (as adjudicated by the doormen) and the party continues until sunrise.

The next day, after a depressingly well received exercise in smugness, featuring Stephen Frears supposedly discussing failure (his hits Dangerous Liaisons and The Queen were, he reveals, "perfect", although he does concede that he can remember failing once, and that it was "horrible"), Jon Hicks performs a tour de force in the same concept. Part Gob Bluth, part Steve Zissou, Hicks flawlessly orchestrates the collapse of his own plastic elephant circus, while occasionally wafting a velvet sheet bearing the words "The Elephant of Surprise". To the side of the stage, Stereolab's Laetitia Sadier stands bemused, having just finished her own stripped back solo set of prettily off-kilter pop songs to a small, but enchanted audience.

In front of a Saturday night audience that might represent the highest concentration of hipness at this year's Port Eliot Festival – no mean feat – Palma Violets blend psych-tinged blues with flashes of Eighties Matchbox-esque fury. Although dynamic and assured, the band seem a little too comfortable with the hype engulfing then, while their songs don't quite possess the fire of the bands they emulate.

Which is probably why there's something reassuring about Toy, a band who seem wary of any fuss. Frontman Tom Dougall twists between discomfort and defiance, as his band's set develops into an absorbing meld of krautrock, surf, post-punk and low budget sci-fi keyboards. By the time their set ends, Dougal's guitar is on the floor and Maxim Barron's bass has stopped working, the night's live action on Caught By the River ending in a wail of thrilling dysfunction.

Sunday's star is Robert Ellis, the Texan invoking Calexico and Mad Men, as well as Merle Haggard and George Jones, during a set of poignant country-folk. He ends with a harrowing, minor-chord bluegrass polemic against the tyranny of his bible-belt upbringing. "You can burn in hell, or sing along", Ellis sings to a crowd silenced and spellbound by a performance which proves once more that Port Eliot has far more to offer than just a pantomime playground for wealthy vacationers and their well turned out children.

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